#robotics Logs

Apr 07 2015

04:51 orlock almost had to call for a tow today
04:52 orlock spot weld in the pedal box thingy busted
04:52 orlock was able to adjust the clutch cable to compensate
04:53 Triffid_Hunter rue_shop3: 3000
04:54 Triffid_Hunter rue_shop3: below 2000 you'll get blobby corners
05:12 SquirrelCZECH again the battery question!
05:12 SquirrelCZECH :D
05:13 SquirrelCZECH what would you suggest as battery for robot that uses 2-3s li-po batteries usually
05:13 SquirrelCZECH (RC Car)
05:13 uirrelCZECH wants something that could be charged without taking it out of the robo
05:13 SquirrelCZECH and something that could last some time without any need to take care of it
05:13 SquirrelCZECH P.S: and batteries with "memory" are out of question too
05:14 uirrelCZECH is not sure that Li-Po is best option
05:15 SquirrelCZECH of course I am willing to take some effort to create entire "System"
05:16 SquirrelCZECH but I want to do it once and don't care for it for some time
05:32 Triffid_Hunter SquirrelCZECH: LiPo is almost definitely the best option
05:33 Triffid_Hunter just make a splitter for the high current and balance connectors and expose them on the outside of the car, with a protector cap to keep dirt out if you desperately want to charge without removing the battery
05:34 Triffid_Hunter SquirrelCZECH: as far as I know, LiPo has the highest energy density AND highest power density of any commonly available battery chemistry
05:34 SquirrelCZECH hmm
05:34 Triffid_Hunter so any other battery of a similar size won't be as fast and won't last as long
05:34 SquirrelCZECH I see
05:35 SquirrelCZECH Triffid_Hunter: btw: just split connectors?
05:36 Triffid_Hunter sure, although I can't imagine what your charger will think of all the car's electronics being live while it's charging
05:36 Triffid_Hunter put a switch on the radio, but leave the ESC direct-connected, switches that can handle that sort of current are expensive and large
05:37 Triffid_Hunter unless your ESC powers the radio, then I dunno
05:39 SquirrelCZECH arduino controls ESC and is going to be powered by it
05:39 SquirrelCZECH nah
05:40 SquirrelCZECH :/
05:59 Triffid_Hunter SquirrelCZECH: http://imgur.com/a/IDQ5u may interest you, it's a little arduino-powered ESC I made
06:03 malinus couldn't you implement multiple ESC's into one mcu though? I've never looked much into how they work, but it looks like people always use 1mcu for each ESC.
06:04 Triffid_Hunter malinus: sure, if you have enough PWM pins available
06:05 Triffid_Hunter malinus: I wanted 10-bit PWM on mine, and the '328 only has one >8bit timer with two output compares
06:05 malinus Triffid_Hunter: how do you do the sensing?
06:07 Triffid_Hunter malinus: what sensing?
06:07 Triffid_Hunter only things I sense are various voltages, and motor current
06:09 malinus Triffid_Hunter: well the position of the brushless motor?
06:09 Triffid_Hunter malinus: ah, mine's for DC brushed, not brushless
06:10 malinus ah okay, why would you even use a dedicated ESC for that?
06:10 Triffid_Hunter malinus: but most ESCs sense the voltage on the undriven winding, the A4960 datasheet is very educational in that regard
06:10 Triffid_Hunter malinus: because I can't push 20A with a bare arduino ;)
06:10 Triffid_Hunter and because when i tried to buy one, there basically weren't any available for a sensible price
06:11 malinus Just a 40A mosfet and a diode
06:11 malinus ?
06:14 Triffid_Hunter malinus: four mosfets (gotta reverse too!)
06:14 Triffid_Hunter and a mosfet gate driver of course, HIP4082 which so far has been absolutely bulletproof and perfectly behaved
06:15 malinus yeah, I don't think there are any "logic level" mosfets that do 40A :)
06:15 Triffid_Hunter malinus: actually there's heaps, IRLB3813, AOT240L, and a stack of others
06:16 Triffid_Hunter malinus: the problem is mostly driving a high-side N and avoiding shoot-through
06:16 Triffid_Hunter malinus: in fact, the AOT240L and IRLB3813 can do 20A with *no heatsink at all*, even a small to moderate heatsink would allow them to hit 40A no worries
06:16 Triffid_Hunter or just use two in parallel
06:17 malinus Nice, where did you get your board made?
06:17 malinus (and what was the price)
06:18 Triffid_Hunter malinus: oshpark, don't recall but probably $20ish at the time for a set of 3
06:18 Triffid_Hunter malinus: there's plenty of cheap options these days.. dirtypcb and elecrow have some ludicrously low prices, prefer oshpark or hackvana if you want someone to care if the board is made wrong
06:22 malinus Cool, thanks
06:22 malinus Triffid_Hunter: you just sodlered it by hand?
06:23 Triffid_Hunter malinus: yes
06:23 Triffid_Hunter the QFN was a little tricky but I managed.. I have paste and hot air for that sort of thing now
06:24 malinus Triffid_Hunter: what's the distance in that package? 0.5mm?
06:24 Triffid_Hunter malinus: yep
07:05 SquirrelCZECH Triffid_Hunter: I've got properly working ESC
07:05 SquirrelCZECH with sensored motor
07:05 SquirrelCZECH I don't see a point in making one than :)
07:06 SquirrelCZECH + it's brushless
09:16 rue_house good show
16:42 beanbag http://hackaday.com/2015/04/07/build-a-phased-array-radar-in-your-garage-that-sees-through-walls/
16:42 beanbag *canuck* me gently
22:49 rue_shop3 armyofevilrobots, aha
22:50 rue_shop3 the X rails are wobbling along the Y axis as the Z goes up and down
22:51 rue_shop3 I think it started about when I noticed that the Z rails were being squeezed by the X carrige and relieved it
22:51 rue_shop3 LOG BOOK!
22:51 rue_shop3 so, I ahve to figure out how to preload the Z axis
23:25 rue_shop3 4 days of chasing ground votlage drop, changing motors and motor drivers, adjusting the hell out of my paramiters
23:25 rue_shop3 and it was slop in a bearing
23:26 perdent Does anyone know what the MinSOP (Minimal Sum of Products) is for this? http://i.gyazo.com/0a6bc2e13e47b1282b77aa64207572e5.png
23:46 rue_shop3 ooo havn'
23:46 rue_shop3 t done a carnograph map in quite a while